Akos Kiss
8dd5186a0d
* First re-style was done automatically by indent to minimize the
chance of errors during rewrite.
* Manual changes were applied to non-critical places only (comments
and spaces):
* Replaced all tabs with spaces.
* Fixed tab stops in formulae in function comments.
(Note: ASCII art for math formulae (especially for super- and
subscripts) is a terrible idea.)
* Unified the style of function comments.
* Moved some in-code comments to their right places, which indent
couldn't handle.
* Added spaces to formulae of in-code comments to make them more
readable.
* Added braces mandated by jerry style guidelines.
* Added parentheses to multiline #ifdef.
JerryScript-DCO-1.0-Signed-off-by: Akos Kiss akiss@inf.u-szeged.hu
77 lines
1.7 KiB
C
77 lines
1.7 KiB
C
|
|
/* @(#)s_scalbn.c 1.3 95/01/18 */
|
|
/*
|
|
* ====================================================
|
|
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
|
|
*
|
|
* Developed at SunSoft, a Sun Microsystems, Inc. business.
|
|
* Permission to use, copy, modify, and distribute this
|
|
* software is freely granted, provided that this notice
|
|
* is preserved.
|
|
* ====================================================
|
|
*/
|
|
|
|
/* scalbn(x,n) returns x* 2**n computed by exponent
|
|
* manipulation rather than by actually performing an
|
|
* exponentiation or a multiplication.
|
|
*/
|
|
|
|
#include "fdlibm.h"
|
|
|
|
#define two54 1.80143985094819840000e+16 /* 0x43500000, 0x00000000 */
|
|
#define twom54 5.55111512312578270212e-17 /* 0x3C900000, 0x00000000 */
|
|
#define huge 1.0e+300
|
|
#define tiny 1.0e-300
|
|
|
|
double
|
|
scalbn (double x, int n)
|
|
{
|
|
int k, hx, lx;
|
|
|
|
hx = __HI (x);
|
|
lx = __LO (x);
|
|
k = (hx & 0x7ff00000) >> 20; /* extract exponent */
|
|
if (k == 0) /* 0 or subnormal x */
|
|
{
|
|
if ((lx | (hx & 0x7fffffff)) == 0) /* +-0 */
|
|
{
|
|
return x;
|
|
}
|
|
x *= two54;
|
|
hx = __HI (x);
|
|
k = ((hx & 0x7ff00000) >> 20) - 54;
|
|
if (n < -50000) /*underflow */
|
|
{
|
|
return tiny * x;
|
|
}
|
|
}
|
|
if (k == 0x7ff) /* NaN or Inf */
|
|
{
|
|
return x + x;
|
|
}
|
|
k = k + n;
|
|
if (k > 0x7fe) /* overflow */
|
|
{
|
|
return huge * copysign (huge, x);
|
|
}
|
|
if (k > 0) /* normal result */
|
|
{
|
|
__HI (x) = (hx & 0x800fffff) | (k << 20);
|
|
return x;
|
|
}
|
|
if (k <= -54)
|
|
{
|
|
if (n > 50000) /* in case integer overflow in n + k */
|
|
{
|
|
return huge * copysign (huge, x); /*overflow */
|
|
}
|
|
else
|
|
{
|
|
return tiny * copysign (tiny, x); /*underflow */
|
|
}
|
|
}
|
|
k += 54; /* subnormal result */
|
|
__HI (x) = (hx & 0x800fffff) | (k << 20);
|
|
return x * twom54;
|
|
} /* scalbn */
|